Submarine cable.



F. JAGUB.

SUBMARINE CABLE. APPLIOATION TILED APR. 30, 1912.

UNITED STATES PATENT OFFICE.

A-G, OF BERLIN, GERMANY, A CORPORATION Os! GERMANY.

sumuanmn ennui.

Specification of Letters Patent. Application med-a n so, 1912. Sci-Jello; sagas.

Toall whom it may concern:

Be it known that I, FRANCIS Jaoon, a British subject, residin at Ellesdene, WestcombeiPark, Kent, ngland, have invented certain new and useful Improve ments in Submarine Cables, ofwhich the following isaspecification, I

My invention relates to submarine cables 9 having a selfidnductive load: distributed unia the line to be thereby compensated. Bothin bare lines and also in cables covered with x ternating currents to be largely increased and the damping action of the capacity of paper and lead such as aroused on land great success-hasbeen obtained by artificially loading the lines with self-induction. It isotherwise in the case of submarine cables when for mechanical and-other'reasons connected with the mode of laying them it is necessary 7 to employ a solid, non-hygroscopic insulating material, 6. g. guttapercha, closely surrounding the conductor. It has been found that in such cables the transmission of speech can be improved only toa very small extent and on only-relativelyshort-lengths by artificially incressing their self-in tion, so that for economic; reasons the construction of marine. cables with increased self-induction had to be desisted iirom in such cases.

A primary object. of my invention is to remedy this defect. "2T0 this end, I employ a material for insulating the conductors which, it-is true, hasheretofore been, used for insulatingpurposes but never in the combination proposed here and for the. pur poses in view in the present case, namely balata.

In order to explain my invention and its importance I shall first refer to the formulae which determine, the performance of telephone lines These formulae are developed by G. Baur in Due elelctrz'sche K abel, 1910, pages 121 and: 124, and by F. Breisig, Theoretische Telegraphic, 1910, pages 282 and 305, and Elclct'rotechnisclw-Zez'tsclw'ift, 1908, [page 588; They arealsoderived from the papers of Pupin, Transaction Amerz'oanlnstitute, Electrical Engineers, 1900, page 245, and Electrical World, 1901, page 5-87, 1902, page 3849 For ordinary lines, '4'. e., lines without artificially increased self-induction, the attenuation constant is calculated from the formula 1. t n/(Anaco- (mo nta ns-AR) The value 5 which appears on the left hand side of the equation represents the attenuation constant of theconductor, which is developed from the Pupin formula for long conductors:

for the end current J a at the end of a conductor of length l (with a given startin current J (See G. Baur Das elekti'zsche Kabel, page 120.) From this formala' it is apparent that the strength of the current at the end of a conductor with a given'starting current becomes greater as [5 becomes smaller. Applied to telephone cables this means that the transmission of the telephonic communication becomes better as 6 becomes smaller or the smaller {5 is the greater can be the length of the cable with letter a means:

o=.2am

in which. n is the frequency or alternations per second of the alternating current transmitted on the conductor. of the telephoniccommunication currents second, so that m on an average is:

w -I2rn= 3.14 8QO=5,000,

in accordance with the international agreement of Paris. The valueA inithehequations means the so-called leaka e conductance and is the same as the Va no a in the Pupin papers. It is measured in the units for conductivity as for example Mk0. A is consequently equal to the conductance per equally good telephonic transmission, The

EB ANGIILZl.0100B, or wns'rcomnn PARK, ENGLAND, assmnon To SIEMENS aEALsKn.

- Patented Oct. 23,1913.

The frequency amounts on an average to about: 11:800. per g w average.

unit length (km) of a conductor of the leakage current circuit formed through the imperfect dielectric and is equal to the reciprocal value of the effective insulation resistance per unit length (km) of the conductor measured with alternating current, of the frequency here stated n equals 800 as an One obtains A in units of Mho if the alternating current insulation resistance measured in ohms is introduced into the computation. By inserting the numerical values of A, C, R and L such as are possessed by an ordinary guttapercha cable, for example, it will be readily understood that the leakage conductance A has hardly any influence at all on the value of [5.

For lines having artificially increased self-induction the damping constants are calculated from the formula R U A E =r /r. 2" c wherein C and A have the same values as in length.

the line without coils; R and L are the values increased by the additional resistance and the additional self-induction for unit All the values hold good as effective loop values for the unit length, 6. g. per kilometer, and in general are referred to an average frequency, generally n:800(m:21m=5,000) I The first term of the right-hand side of Equation II for [5 contains the values of the resistance, capacity and self-induction; this term decreases as the self-induction increases and becomes smaller as the resistance of the loop is reduced. The second term contains the leakage conductance and also the capacity and self-induction; its value, however, bccomes greater as the self-induction increases and increases, in addition, as the leakage conductance becomes greater. From this comparison of the two members of the equation it can be seen that when the selfinductive load is made great, the second member can be considerably greater than the first, particularly if the leakage conductance assumes a large value. If the leakage conductance be small, on the contrary, as e. g. in lead-paper cables, the leakage conductance member can be brought into a suitable relation to the resistance member, even if it is a matter of a thick conductor. By leakage conductance is understood, as is well-known, the reciprocal value of -the effective alternating-current insulation for a given frequency, 6. g.

n=800(m=2un:5,000)

As the value of the leakage conductance depends, of course, on the thickness of the layer of insulation, thus on the capacity, it is necessary to state the value of the leakage conductance for a given capacity, preferably unit capacity, thus the valndA/C. This is preferable also because investigations heretofore made have shown that for a given material and frequency this magnitude remains approximately constant, is thus independent of the thickness of the layer of insulation and can therefore be looked upon as a kind of material constant. Now whereas modern paper-covered cables, such as are used for underground cables, have values of A/C which fluctuate between approximately 10 and 40, submarine cables having guttapercha insulation have a value of A/C fluctuating approximately about 100. .This exceedingly high value of A/C is the cause of the above-mentioned economic failure when employing submarine cables having an artificial self-inductive load. It has been attempted to obviate this defect by making guttapercha cables in which the conductor was surrounded under the g ttapercha coverlng with paper-air lnsulatlon.

A usable form of this construction was also obtained. The construction had,.however, the defect of small mechanical resistance which rendered its general employment difiicult. I therefore attempted to discover a solid, non-hygroscopic material having leakage conductance values similar to those of the paper-air insulation which had proved satisfactory. Careful tests have shown that insulation having such properties is to be found in the material obtainable on the market under the name of balata and heretofore employed as an addition to or a substitute for guttapercha for insulating conductors. My investigations have shown that I in pure balata the value of A/C fluctuates approximately about 10. As balata can be worked as easily as guttapercha and is not inferior to it in mechanical strength, it enables long submarine cables for the first time to be successfully loaded artificially with self-induction. A submarine cable constructed in this manner will have for A/C approximately the same values as an underground cable having paper-air insulation.

Slight impurification ofthe balata or small admixtures of guttapercha would not affect this action of the balata when employed in submarine cables loaded with self-induction, in so far as the value of A/C is not considerably influenced. Its use for this purpose will not be practically affected, as long as the value A/C does not rise above 40. The same favorable action as in transmission between telephone stations will be obtained by means of balata when employed in the described manner in the transmission of telegraphic currents having a rapid succession of impulses. e

One illustrative embodiment of my invention is represented by way of example in the accompanying drawings, in which- Figure 1 shows in side view, with successive layers broken away, and Fig. 2 shows in transverse section my improved cable.

Referring to the drawing, a designates the conductors and b the insulation composed of balata surrounding the same.

0 shows.an iron wire armor and d, d jute wrappings.

The enlargement X indicates the Pupin coil.

I claiinz- A submarine cable comprising in combination a plurality of conductors, an artificial self-induction load thereon, and insulation composed of balata, closely surrounding each of said conductors for the specified.

In testimony whereof, I have signed my name to this specification in the presence of two witnesses.

FRANCIS JACOB.

Witnesses:

T. J. HUGHES, GEO. HENNIG.

purpose 1 5 

